Electrical switches are among the oldest and most commonly used electrical components found in use today. In spite of many years of technological advancement and development, however, a need still exists to improve electrical and mechanical switch characteristics such as insertion loss, reliability, cross coupling, cost, physical size and upper signal frequency limit. Typically, attempts to improve one characteristic result in a tradeoff that impairs another characteristic. For example, if an attempt is made to reduce manufacturing cost by reducing size, the high frequency isolation or signal cross-coupling characteristic deteriorates and the insertion loss increases. There thus exists a need for continuing improvement in the design and manufacture of electrical switches.
Present day electrical switches typically utilize some kind of spring loaded center contact that may be flexed or otherwise moved between different contact positions to provide a desired switching arrangement. U.S. Pat. No. 2,958,054 to Concelman for "Impedance Terminated Coaxial Line Switch Apparatus" teaches a relay switch arrangement in which unconnected terminals are terminated in their characteristic impedance to reduce the voltage standing wave ratio (VSWR) and hence cross talk inducing signal magnitudes. In that patent, spring biased flexure members 23, 24 extend from opposite side conductors toward a center conductor where they are moved by actuator pins 31, 32 to engage either a center conductor or a termination resistor.
U.S. Pat. No. 3,182,270 to Horton for "Multiple Position Coaxial Switch With Angularly Spaced Radial Channels" discloses a multiple pole switch in which each side terminal is selectively coupled by a spring biased flexure element 23 to either a center contact or a terminating resistor under control of a relay coil. Such an arrangement has a relatively high parts count and hence high expense, is subject to component failure and does not have a geometric configuration that minimizes insertion loss or VSWR.
U.S. Pat. No. 4,070,637 to Assal et al. for "Redundant Microwave Configuration" teaches a microwave frequency switch arrangement in which any one of a plurality of terminals may be connected to any other terminal. The switch uses nonflexing strip line contacts which are free at each end and are moved into or out of contact with adjacent contact points. Each end of the moveable strip line center contact selectively engages or disengages a single contact point.
U.S. Pat. No. 4,298,847 to Hoffman for "Multiposition Microwave Switch With Independent Termination" teaches another multipole switch arrangement in which both ends disengage a corresponding fixed contact under control of a solenoid.